A scanning probe microscope (SPM) is used to measure fine shapes and properties of the surface of a sample. The scanning probe microscope brings a probe close to the sample to measure an atomic force (attraction and repulsion), tunnel current, and other physical phenomena between the probe and the sample. The scanning probe microscope can thus measure the shapes and properties of the surface of the sample at the atomic level.
The scanning probe microscope described in Patent Document 1 includes a cantilever and a probe provided at the distal end of the cantilever. In such a scanning probe microscope, upward and downward movements of the probe are measured by illuminating the rear side of the cantilever with laser light and measuring the laser light reflected off the rear side of the cantilever. That is, the motion of the cantilever affects the measurement accuracy of the probe.
A scanning probe microscope is used in a vacuum environment in many cases. Numerical simulation analysis has conventionally been performed on vibration/deformation characteristics of a cantilever alone in a vacuum or atmospheric environment.
On the other hand, objects measured under a scanning probe microscope have diversified into many types. For example, it is necessary in the biological field to measure objects in aqueous solutions. The atomic force microscope (AFM) described in Patent Document 2 measures a sample in a solution. Vibration/deformation characteristics of a cantilever in an aqueous solution may change when a large fluid drag force is applied to the cantilever.
No comprehensive numerical simulation has been made on a cantilever of an atomic force microscope when the cantilever is immersed in an aqueous solution. Only interaction between a probe at the distal end of the cantilever and a sample or a substrate has been computed. The sample is placed on the substrate, and the probe measures a shape of the sample present on the substrate.
Although a large number of numerical simulations have been made on fluids, they have not been considered in combination with elastic deformation of a cantilever, which is an obstacle for a fluid.
In conventional numerical simulations, the contact height indicating the position where the probe comes into contact with a sample is handled as a measurement value that directly relates to a measurement signal. An actual measurement signal, however, represents the position of the spot of reflected laser light with which the distal end of the cantilever is illuminated. That is, conventional numerical simulations do not conform to actual measurement situations.    Patent Document 1: Japanese Laid-Open Patent Publication No. 5-71951    Patent Document 2: Japanese Laid-Open Patent Publication No. 11-118813